For this purpose, appropriate cuts or score marks are usually produced in a large glass plate with a cutting wheel or a needle and the glass is then mechanically broken at these desired breaking lines. The breaking operation can then be realized by hand or by means of a mechanical apparatus. The mechanical breaking operation is here difficult to control, since the breaking occurs abruptly. With such methods, it can therefore sometimes happen that the break takes a different course from that which is desired and the glass breaks at a different breaking line.
From the patent literature of DE 10 2005 054 669 A1, the solution to the problem is therefore based on developing a method in which the glass to be cut breaks only at the desired line.
This object is achieved by virtue of the fact that a method for breaking glass and ceramic, which method is characterized in that glass is broken at a marked site by means of ultrasound, is claimed.
According to this printed document, it can further be provided that said method is characterized in that the glass, for the purpose of the desired separation, has first been cut at a specific line with a cutting wheel, scored with a needle or cut with a laser.
An apparatus for implementing such a method cannot be derived from this printed document. Nor is there here any proposal for the design of a plant for machining precuts of glass plates on an industrial scale.
In addition, a method for the laser thermal separation of flat glass plates is known from DE 10 2004 014 277 A1. The object of this invention is to make thermal markings in glass plates along predefined desired breaking lines and, at the same time, to be able to pursue higher cutting speeds (significantly greater than 1 m/min). In particular, good-quality glasses of relatively large thickness should also be able to be separated and even very thick glasses (about 20 mm) should be scored sufficiently deeply. All this should also be achieved in respect of curved cuts.
For the achievement of this object, in this printed document a method for separating flat glass plates by thermal scoring by means of a laser beam is claimed, which laser beam, in the form of a beam spot, is moved along a desired separation line at a chosen rate of advance over the glass surface. Furthermore, that line region on the glass surface which has thus been laser-heated is here cooled by a tracking cooling nozzle, wherein beforehand, in the or shortly before the starting region of the desired separation line, an initial invasion of the glass surface in the form of a mechanically or otherwise produced scoring point is made and wherein, after the thermal scoring, the glass proceeds to be broken. This described method is characterized in that the guidance of the laser beam along the desired separation line is realized in the form of a repetitive frequent sweep along the desired separation line by means of a rapidly scanned laser beam.
In such a laser thermal separating method, on all sides of a glass plate microcracks are avoided on the edges. Such a glass plate is therefore elastically deformable to a greater degree than a glass plate which has been cut to size in a normal way.
Apart from a basic sketch (shown in FIG. 4 of said document) of an apparatus for cutting flat glass plates, no allusions to a constructional design of the described method can be derived from DE 10 2004 014 277 A1. In particular, this printed document clearly focuses on the scientific investigation of such a method. The industrial use of such a method constitutes a quite different object, however.
U.S. Pat. No. 489,908 A discloses a method and an apparatus for automatically separating a moving glass ribbon along a traced line, consisting of a light source directed at the glass ribbon and a photocell which scans the glass ribbon. The separation of large-format glass plates by means of laser beams is not possible herewith.
In addition, U.S. Pat. No. 6,722,250 B2 discloses a method for continually cutting to length pre-cuts from a continuously moved endless material, in which the optical detection of the scribed line by means of red-light lighting and the registration by means of a camera is indicated. With this method, however, elastically deformable large-format glass plates cannot be separated on an industrial scale and in a failsafe manner.
Moreover, such methods have hitherto been used only to cut small glass areas, such as glass plates for protecting mobile phone displays.